I fail to see why anyone would expect their carrier to facilitate unlocking of a phone they have subsidised, until the contract with which the phone was supplied expires.
On the other hand I do not see how the carrier is in need of this protection, as they get paid for the phone in any case ..... over the length of the contract or by an early termination fee.
Any info on what this is designed to discourage?
Well in Ireland networks / carriers are very cool about it. I am with Vodafone network and they don't care if I unlock the phone. They will do it for me without a problem too if I am eligible.
For example: I had Nokia 6610i in the past and was using it for 5 or 6 months and asked them about unlocking it - they said no problem You have topped up by €120 in the last 6 months we will order the unlocking code from Nokia and we will text You when we have it...
And that's cool but someone would say... hmmm €120 is a lot of money - sure it is but if I top up by €20 a month I get unlimited free texts and calls to every single Vodafone mobile 24/7 for the next 30 days AND here is the nice part - sometime after I have bought two Nokias 5200 (for myself and my fiance) as a upgrade (no sim card just the phone) - I paid €100 for each and I got €80 free call / text credit - €10 for purchasing (applied right after my simcard was placed in the phone), €10 for registering the phone with my vodafone.ie account and then €10 each month for six months BUT right after I have purchased them we had to travel to Poland and we wanted to use Polish sim cards in them. So I rang Vodafone and they have unlocked the phones for us... because my sim card was in the new phone they checked and said - yes you are a valuable customer, you have the same number for x years and you have been topping up regularly - there You go - here are your unlocking codes... Voila... Same thing happened when I purchased my Nokia N73...
That's how You treat the customers and make sure they don't go with another carrier...
I am not sure how other phones are getting unlocked - I know that Nokia will work with the unlocking codes, other phones need to be re-flashed with new software I guess.
I think recently they changed their policy to "You can unlock 5 phones per 1 number / simcard" but I am sure it's just to make life tougher for all those folks that are purchasing upgrade phones, unlocking them, registering, selling on while they still receive free credit using their old phone... I am betting that customers like myself could still ring them up and they would unlock the phone for me.